So because it was $5 off, and she paid 80% of the original price, that would mean it would have been 20% off. That means 20% = $5. Multiply that by 5 to get to 100% and you find that the shirt is $25 originally. Then you can either multiply that 20% = $5 by 4 to get 80%, or just subtract $5 from the full price. That means Selina paid $20 for the shirt.
